Method and apparatus for performing handover in wireless communication system

ABSTRACT

A method for and apparatus for performing handover in a wireless communication system is provided. A wireless device transmits measurement results configured for a secondary radio access technologies (RAT) system, receives information on routing modification based on the measurement results, from a network entity of a primary RAT system and performs a handover to a target access network according to the information on routing modification. The secondary RAT system is used for a user plane (U-plane) data, and the handover is determined based on at least one of a quality of service (QoS) information, load information about the primary RAT system and secondary RAT system, and a network preference information of the UE.

This application is a 35 USC § 371 National Stage entry of InternationalApplication No. PCT/KR2014/005646 filed on Jun. 25, 2014, and claimspriority to U.S. Provisional Application No. 61/841,938 filed on Jul. 2,2013, all of which are hereby incorporated by reference in theirentireties as if fully set forth herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to wireless communications, and morespecifically, to a method and apparatus for performing handover in awireless communication system.

Related Art

With the recent trend of increasing high-rate data traffic, fifthgeneration mobile communication technologies are in discussion for theirrealistic and efficient backup. One of requirements for fifth generationmobile communication technologies is the interworking betweenheterogeneous wireless communication systems, particularly between acellular system and a wireless local area network (WLAN) system. Thecellular system may be one of a 3rd generation partnership project(3GPP) long-term evolution (LTE) system, a 3GPP LTE-A (advanced) system,and an institute of electrical and electronics engineers (IEEE) 802.16(WiMax, WiBro) system. The WLAN system may be an IEEE 802.11 (Wi-Fi)system. In particular, WLAN is a wireless communication system that iscommonly used for various user equipments, and thus, the cellular-WLANinteroperation is a high-priority convergence technique. Offloading bythe cellular-WLAN interoperation may increase the coverage and capacityof the cellular system.

The arrival of the ubiquitous environment led to a sharp increase indemands for seamless services anytime, anywhere. The fifth generationmobile communication system may adopt a plurality of radio accesstechnologies (RATs) for always gaining easy access and maintainingefficient performance in any place. In other words, the fifth-generationmobile communication system may use multiple RATs in a converging mannerthrough the interoperation between heterogeneous wireless communicationsystems. Each entity in the plurality of RATs constituting afifth-generation mobile communication system may exchange informationtherebetween, and accordingly, the optimal communication system may beprovided to a user in the fifth-generation mobile communication system.Among the plurality of RATs constituting the fifth-generation mobilecommunication system, a specific RAT may operate as a primary RATsystem, and another specific RAT may operate as a secondary RAT system.That is, the primary RAT system may mainly play a role to provide acommunication system to a user in the fifth-generation mobilecommunication system, while the secondary RAT system may assist theprimary RAT system.

In general, a 3GPP LTE(-A) or IEEE 802.16 cellular system withrelatively broad coverage may be a primary RAT system, and a Wi-Fisystem with relatively narrower coverage may be a secondary RAT system.

In general, in an interworking system of the cellular system and theWLAN system, all data flows transmitted/received through a secondary RATsystem (e.g., Wi-Fi system) as well as a primary RAT system (e.g.,cellular system) may be controlled by a device operating as a localmobility anchor (LMA). When a session for the Wi-Fi system alreadyexists, a need for performing seamless handover for the cellular systemmay be required for simultaneous transmission.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for performinghandover in a wireless communication system. The present invention alsoprovides a method and apparatus for transmitting/receiving informationon routing modification in a wireless communication system.

In an aspect, a method for performing, by a user equipment (UE),handover in a wireless communication system is provided. The methodincludes transmitting measurement results configured for a secondaryradio access technologies (RAT) system, receiving information on routingmodification based on the measurement results, from a network entity ofa primary RAT system, and performing a handover to a target accessnetwork according to the information on routing modification. Thesecondary RAT system is used for a user plane (U-plane) data, and thehandover is determined based on at least one of a quality of service(QoS) information, load information about the primary RAT system andsecondary RAT system, and a network preference information of the UE.

In another aspect, a wireless device in a wireless communication systemis provided. The wireless device includes a radio frequency (RF) unitfor transmitting or receiving a radio signal, and a processor coupled tothe RF unit, and configured to transmit measurement results configuredfor a secondary radio access technologies (RAT) system, receiveinformation on routing modification based on the measurement results,from a network entity of a primary RAT system, and perform a handover toa target access network according to the information on routingmodification. The secondary RAT system is used for a user plane(U-plane) data, and the handover is determined based on at least one ofa quality of service (QoS) information, load information about theprimary RAT system and secondary RAT system, and a network preferenceinformation of the UE.

The embodiment of the present invention supports data and controltransmission efficiency with dynamic cellular data flow sessions.Especially, the embodiment of the present invention supports seamlesshandover using routing information in interworking system havingcellular and Wi-Fi environments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system to which the presentinvention is applied.

FIG. 2 shows an example of a radio frame structure to which the presentinvention is applied.

FIG. 3 shows a wireless local area network (WLAN) system which thepresent invention is applied.

FIG. 4 shows an example of a frame structure of WLAN system which thepresent invention is applied.

FIG. 5 shows an example of a scenario of a converged communicationsystem of a cellular system and a Wi-Fi system.

FIG. 6 shows an example of IP flow mobility in a converged communicationsystem of a cellular system and a Wi-Fi system.

FIG. 7 shows another example of IP flow mobility in a convergedcommunication system of a cellular system and a Wi-Fi system.

FIG. 8 and FIG. 9 show methods for transmitting and receiving a messageto change routing information according to an embodiment of the presentinvention.

FIG. 10 to FIG. 15 show examples of changing routing informationaccording to an embodiment of the present invention.

FIG. 16 is a block diagram showing a wireless communication systemaccording to an embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A technology below can be used in a variety of wireless communicationsystems, such as code division multiple access (CDMA), frequencydivision multiple access (FDMA), time division multiple access (TDMA),orthogonal frequency division multiple access (OFDMA), and singlecarrier frequency division multiple access (SC-FDMA). CDMA can beimplemented using radio technology, such as universal terrestrial radioaccess (UTRA) or CDMA2000. TDMA can be implemented using radiotechnology, such as global system for mobile communications(GSM)/general packet radio service (GPRS)/enhanced data rates for GSMevolution (EDGE). OFDMA can be implemented using radio technology, suchas IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, or EvolvedUTRA (E-UTRA). IEEE 802.16m is the evolution of IEEE 802.16e, and itprovides a backward compatibility with an IEEE 802.16e-based system.UTRA is part of a universal mobile telecommunications system (UMTS). 3rdgeneration partnership project (3GPP) long term evolution (LTE) is partof evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access(E-UTRA), and it adopts OFDMA in downlink (DL) and SC-FDMA in uplink(UL). LTE-A (advanced) is the evolution of 3GPP LTE.

3GPP LTE(-A) and IEEE 802.11 are chiefly described as an example inorder to clarify the description, but the technical spirit of thepresent invention is not limited to 3GPP LTE(-A) and IEEE 802.11.

FIG. 1 shows a wireless communication system to which the presentinvention is applied.

Referring to FIG. 1, the cellular system 10 includes one or more basestations (BSs) 11. The BSs 11 provide communication services torespective geographical areas (in general called ‘cells’) 15 a, 15 b,and 15 c. Each of the cells can be divided into a number of areas(called ‘sectors’). A user equipment (UE) 12 can be fixed or mobile andmay be referred to as another terminology, such as a mobile station(MS), a mobile terminal (MT), a user terminal (UT), a subscriber station(SS), a wireless device, a personal digital assistant (PDA), a wirelessmodem, or a handheld device. In general, the BS 11 refers to a fixedstation that communicates with the UEs 12, and it may be referred to asanother terminology, such as an evolved-NodeB (eNB), a base transceiversystem (BTS), or an access point.

The UE generally belongs to one cell. A cell to which a UE belongs iscalled a serving cell. A BS providing the serving cell withcommunication services is called a serving BS. A wireless communicationsystem is a cellular system, and so it includes other cells neighboringa serving cell. Other cells neighboring the serving cell are calledneighbor cells. A BS providing the neighbor cells with communicationservices is called as a neighbor BS. The serving cell and the neighborcells are relatively determined on the basis of a UE.

This technology can be used in the downlink (DL) or the uplink (UL). Ingeneral, DL refers to communication from the BS 11 to the UE 12, and ULrefers to communication from the UE 12 to the BS 11. In the DL, atransmitter may be part of the BS 11 and a receiver may be part of theUE 12. In the UL, a transmitter may be part of the UE 12 and a receivermay be part of the BS 11.

FIG. 2 shows an example of a radio frame structure to which the presentinvention is applied.

Referring to FIG. 2, the radio frame includes 10 subframes, and onesubframe includes two slots. The slots in the radio frame are numberedby #0 to #19. A transmission time interval (TTI) is a scheduling unitfor a data transmission. In 3GPP LTE, one TTI may be identical with atime taken for transmitting one subframe. A radio frame may have alength of 10 ms, a subframe may have a length of 1 ms, and a slot mayhave a length of 0.5 ms.

One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in a time domain and a plurality ofsubcarriers in a frequency domain. Since 3GPP LTE uses OFDMA indownlink, the OFDM symbols are used to express a symbol period. The OFDMsymbols may be called by other names depending on a multiple-accessscheme. For example, when a single carrier frequency division multipleaccess (SC-FDMA) is in use as an uplink multi-access scheme, the OFDMsymbols may be called SC-FDMA symbols. A resource block (RB), a resourceallocation unit, includes a plurality of continuous subcarriers in aslot. The structure of the radio frame is merely an example. Namely, thenumber of subframes included in a radio frame, the number of slotsincluded in a subframe, or the number of OFDM symbols included in a slotmay vary. 3GPP LTE defines that one slot includes seven OFDM symbols ina normal cyclic prefix (CP) and one slot includes six OFDM symbols in anextended CP.

FIG. 3 shows a wireless local area network (WLAN) system which thepresent invention is applied. The WLAN system may also be referred to asa Wi-Fi system.

Referring to FIG. 3, the WLAN system includes one access point (AP) 20and a plurality of stations (STAs) 31, 32, 33, 34, and 40). The AP 20may be linked to each STA 31, 32, 33, 34, and 40 and may communicatetherewith. The WLAN system includes one or more basic service sets(BSSs). The BSS is a set of STAs that may be successfully synchronizedwith each other and may communicate with each other, and does not mean aspecific region.

An infrastructure BSS includes one or more non-AP stations, APs thatprovide a distribution service (DS), and a DS that links a plurality ofAPs with each other. In the infrastructure BSS, an AP manages non-APSTAs of the BSS. Accordingly, the WLAN system shown in FIG. 3 mayinclude an infrastructure BSS. In contrast, an independent BSS (IBSS) isa BSS that operates in ad-hoc mode. The IBSS does not include an AP andthus lacks a centralized management entity. That is, in the IBSS, thenon-AP STAs are managed in a distributed manner. The IBSS may have allthe STAs constituted of mobile STAs and is not allowed to access thedistribution system, thus achieving a self-contained network. The STA israndom functional medium that includes a physical layer interface for awireless medium and a media access control (MAC)) observing IEEE 802.11standards, and in its broader concepts, it includes both the AP andnon-AP station.

The non-AP STA is an STA, not an AP. The non-AP STA may also be referredto as a mobile terminal, a wireless device, a wireless transmit/receiveunit (WTRU), a user equipment (UE), a mobile station (MS), a mobilesubscriber unit or simply as a user. Hereinafter, for ease ofdescription, the non-AP STA denotes an STA.

The AP is a functional entity that provides access to a distributionsystem via a wireless medium for an STA associated with the AP. In theinfrastructure BSS including an AP, communication between STAs isbasically done via an AP, but in case a direct link is established,direct communication may be achieved between STAs. The AP may also bereferred to as a central controller, a base station (BS), a NodeB, abase transceiver system (BTS), or a site controller.

A plurality of infrastructure BSSs may be linked with each anotherthrough a distribution system. The plurality of BSSs linked with eachanother is referred to as an extended service set (ESS). The APs and/orSTAs included in the ESS may communicate with each other, and in thesame ESS, an STA may move from one BSS to another, while in seamlesscommunication.

FIG. 4 shows an example of a frame structure of WLAN system which thepresent invention is applied. A frame of WLAN system includes a set offields in a fixed order.

Referring to FIG. 4, the frame includes a frame control field, aduration/ID field, an address 1 field, an address 2 field, an address 3field, a sequence control field, an address 4 field, a quality ofservice (QoS) control field, an HT control field, a frame body field,and a frame check sequence (FCS) field. Among the fields listed above,the frame control field, the duration/ID field, the address 1 field, andthe FCS field constitute a minimum frame format, and may be included inall IEEE 802.11 frames. The address 2 field, the address 3 field, thesequence control field, the address 4 field, the QoS control field, theHT control field, and the frame body field may be included only in aspecific frame type.

The frame control field may include various subfields. The duration/IDfield may be 16 bits in length. The address field may include a basicservice set identifier (BSSID), a source address (SA), a destinationaddress (DA), a transmitting STA address (TA), and a receiving STAaddress (RA). In the address field, different fields may be used forother purposes according to a frame type. The sequence control field canbe used when fragments are reassembled or when an overlapping frame isdiscarded. The sequence control field may be 16 bits, and may includetwo subfields indicating a sequence number and a fragment number. TheFCS field can be used to check an error of a frame received by astation. The FCS field may be a 32-bit field including a 32-bit cyclicredundancy check (CRC). An FCS can be calculated across the frame bodyfield and all fields of a media access control (MAC) header.

The frame body field may include information specified for an individualframe type and subtype. That is, the frame body field carries high-leveldata from one station to another station. The frame body field can alsobe called a data field. The frame body field can be variously changed inlength. A minimum length of the frame body field may be zero octet. Amaximum length of the frame body field may be determined by a total sumof a maximum length of a MAC service data unit (MSDU), a length of amesh control field, and an overhead for encryption or a total sum of amaximum length of an aggregated MSDU (A-MSDU) and an overhead forencryption. The data frame includes high-level protocol data of theframe body field. The data frame may always include the frame controlfield, the duration/ID field, the address 1 field, the address 2 field,the address 3 field, the sequence control field, the frame body field,and the FCS field. A presence of an address 4 field may be determined bya configuration of a ‘To DS’ subfield and a ‘From DS’ subfield in theframe control field. Another data frame type can be categorizedaccording to a function.

A management frame may always include the frame control field, theduration/ID field, the address 1 field, the address 2 field, the address3 field, the sequence control field, the frame body field, and the FCSfield. Data included in the frame body field generally uses afixed-length field called a fixed field and a variable-length fieldcalled an information element. The information element is avariable-length data unit.

The management frame can be used for various purposes according to asubtype. That is, a frame body field of a different subtype includesdifferent information. A beacon frame reports an existence of a network,and takes an important role of network maintenance. The beacon framecorresponds to a parameter which allows a mobile station to participatein the network. In addition, the beacon frame is periodicallytransmitted so that the mobile station can scan and recognize thenetwork. A probe request frame is used to scan a network in which themobile station exists. A probe response frame is a response for theprobe request frame. An authentication request is used so that themobile station requests an access point to perform authentication. Anauthentication response frame is a response for the authenticationrequest frame. A de-authentication frame is used to finish anauthentication relation. An association request frame is transmitted sothat the mobile station participates in the network when the mobilestation recognizes the compatible network and is authenticated. Anassociation response frame is a response for the association requestframe. A de-association frame is used to finish an association relation.Three states may exist according to an authentication and associationprocedure as shown Table 1.

TABLE 1 Authentication Association State 1 X X State 2 ◯ X State 3 ◯ ◯

To transmit a data frame, a device must perform the authentication andassociation procedure with respect to a network. In Table 1, a procedureof transitioning from the state 1 to the state 2 can be called theauthentication procedure. The authentication procedure can be performedin such a manner that one device acquires information on a differentdevice and authenticates the different device. The information on thedifferent device can be acquired by using two methods, i.e., a passivescanning method for acquiring information on a different node byreceiving a beacon frame and an active scanning method for acquiring theinformation on the different device by transmitting a probe requestmessage and receiving a probe response message received in responsethereto. The authentication procedure can be complete by exchanging anauthentication request frame and an authentication response frame.

In Table 1, a procedure of transitioning from the state 2 to the state 3can be called the association procedure. The association procedure canbe complete when two devices exchange the association request frame andthe association response frame upon completion of the authenticationprocedure. An association ID can be allocated by the associationprocedure.

FIG. 5 shows an example of a scenario of a converged communicationsystem of a cellular system and a Wi-Fi system.

It is assumed in FIG. 5 that the cellular system operates as a primaryRAT system of the converged communication system, and the Wi-Fi systemoperates as a secondary RAT system of the converged communicationsystem. Further, the cellular system may be a 3GPP LTE(-A) system.Hereinafter, for ease of description, it is assumed that the primary RATsystem of the converged communication system is a 3GPP LTE(-A) system,and the secondary RAT system of the communication system is an IEEE802.11 system, i.e., a Wi-Fi system. However, embodiments of the presentinvention are not limited thereto.

Referring to FIG. 5, there are a plurality of general devices 561, 562,563, 564, and 565 in the coverage of the cellular base station 550. Eachof the general devices 561, 562, 563, 564, and 565 may be a userequipment in a cellular system. The cellular base station 550 maycommunicate with each of the general devices 561, 562, 563, 564, and 565via a cellular radio interface. For example, the cellular base station550 may perform voice call communication with each of the generaldevices 561, 562, 563, 564, and 565 or may control access of eachgeneral device 561, 562, 563, 564, and 565 to a Wi-Fi system.

The cellular base station 550 is connected to a serving gateway(S-GW)/mobility management entity (MME) 570 through a cellular systeminterface. The MME contains a user equipment's access information orinformation on a user equipment's capability, and such information maybe mainly used for mobility management. The MME is in charge of acontrol plane. The S-GW is a gateway having an E-UTRAN as an end point.The S-GW is in charge of a user plane. The S-GW/MME 570 is connected toa packet data network (PDN) gateway (P-GW) 571 and a home subscriberserver (HSS) 572 through the cellular system interface. The PDN-GW is agateway having a PDN as an end point.

The P-GW 571 and the HSS 572 are connected to a 3GPP accessauthentication authorization (AAA) server 573 through the cellularsystem interface. The P-GW 571 and the 3GPP AAA server 573 may beconnected to an evolved packet data gateway (ePDG) 574 through thecellular system interface. The ePDG 574 may be included only inun-trusted non-3GPP access. The ePDG 574 may be connected to a WLANaccess gateway (WAG) 575. The WAG 575 may be in charge of a P-GW in aWi-Fi system.

Meanwhile, a plurality of APs 581, 582, and 583 may be present in thecoverage of the cellular base station 550. Each of the APs 581, 582, and583 may have coverage which is shorter than that of the cellular basestation 550. Each of the APs 581, 582, and 583 may communicate withgeneral devices 561, 562, and 563 that are present in its coveragethrough a Wi-Fi radio interface. In other words, the general devices561, 562, and 563 may communicate with the cellular base station 550and/or APs 581, 582, and 583. Communication methods of the generaldevices 561, 562, and 563 are as follows:

1) Cellular/Wi-Fi simultaneous radio transmission: the general device561 may perform high-speed data communication with the AP 581 through aWi-Fi radio interface while communicating with the cellular base station550 through a cellular radio interface.

2) Cellular/Wi-Fi user plane automatic shift: the general device 562 maycommunicate with one of the cellular base station 550 and the AP 582 byuser plane automatic shift. At this time, the control plane may bepresent in both the cellular system and the Wi-Fi system or only in thecellular system.

3) Terminal cooperative transmission: the general device 564 operatingas a source device may directly communicate with the cellular basestation 550 through a cellular radio interface or may indirectlycommunicate with the cellular base station 550 through a general device565 operating as a cooperative device. That is, the cooperative device565 may assist the source device 564 so that the source device 564 mayindirectly communicate with the cellular base station 550 throughitself. The source device 564 and the cooperative device 565 communicatewith each other through a Wi-Fi radio interface.

4) Wi-Fi-based cellular link control mechanism: the AP 583 may perform acellular link control mechanism such as paging or location registrationof a network for the cellular general device 563. The general device 563is not directly connected to the cellular base station 550 and maydirectly communicate with the cellular base station 550 thorough the AP583.

Each of the APs 581, 582, and 583 is connected to the WAG 575 through aWi-Fi system interface.

In general, in an interworking system of the cellular system and theWLAN system, all data flows may be transmitted and/or receivedsimultaneously through a plurality of RAT systems (e.g., primary RATsystem, secondary RAT system). In addition, all data flowstransmitted/received through a secondary RAT system (e.g., Wi-Fi system)as well as a primary RAT system (e.g., cellular system) may becontrolled by a device operating as a local mobility anchor (LMA). Forexample, data to be transmitted through a cellular system and data to betransmitted through a Wi-Fi system always go through the P-GW. That is,in FIG. 5, a device serving as an LMA may be the P-GW. In this regard, aterm “LMA” used in a proxy mobile Internet protocol (PMIP) protocol maybe called a different term in another protocol, such as home agent (HA).

When data flows are transmitted through the plurality of RAT systemssimultaneously in the converged communication system of the cellularsystem and the Wi-Fi system, scenarios for simultaneous transmission maybe classified into a user plane (U-plane) separation for the same dataflow (or, bandwidth/U-plane aggregation) and U-plane separation fordifferent data flows (or, bandwidth/U-plane segregation).

FIG. 6 shows an example of IP flow mobility in a converged communicationsystem of a cellular system and a Wi-Fi system. FIG. 6 shows U-planeseparation for the same data flow, i.e., bandwidth/U-plane aggregation.

Referring to FIG. 6, IP packets for flow 1 include IP packets 1, 2, and3, and IP packets for flow 2 include IP packets 4, 5, 6, and 7. The P-GWis connected to a PDN 1, and operates as an LMA. That is, all IP packetsare transmitted to a UE through the P-GW. The IP packet 1 in the IPpacket for flow 1 is transmitted to the UE through the Wi-Fi system bygoing through an ePDG and/or a WAG, and IP packets 2 and 3 aretransmitted to the UE through the cellular system by going through a BS.In this case, the ePDG or the WAG may be a mobile access gateway (MAG)in the Wi-Fi system, and the BS may be a MAG in the cellular system. Inthe IP packet for flow 2, the IP packets 5 and 6 are transmitted to theUE through the Wi-Fi system by going through the PDG and/or the WAG, andIP packets 4 and 7 are transmitted to the UE through the cellular systemby going through the BS. That is, IP packets for different flows areaggregated each other.

FIG. 7 shows another example of IP flow mobility in a convergedcommunication system of a cellular system and a Wi-Fi system. The FIG. 7shows U-plane separation for different data flows, i.e.,bandwidth/U-plane segregation.

Referring to FIG. 7, IP packets for flow 1 include IP packets 1, 2, and3, and IP packets for flow 2 include IP packets 4, 5, 6, and 7. The P-GWis connected to a PDN 1, and operates as an LMA. That is, all IP packetsare transmitted to a UE through the P-GW. The IP packets for flow 1 aretransmitted to the UE through the cellular system by going through a BS.In this case, the BS may be an MAG in the cellular system. The IPpackets for flow 2 are transmitted to the UE through the Wi-Fi system bygoing through the ePDG and/or the WAG. In this case, the ePDG or the WAGmay be an MAG in the Wi-Fi system. That is, IP packets for differentflows are segregated each other.

In scenarios for simultaneous transmission, a method for establishing,by a network, a session to support seamless connectivity for data flowsmay be required. Accordingly, according to an embodiment of the presentinvention, a method for establishing, under the control of a primary RATsystem, a data flow session for the same PDN in the primary RAT systemis described. In a following description, it is assumed that the primaryRAT system is a 3GPP LTE system and the secondary RAT system is a Wi-Fisystem, but the present invention is not limited thereto. In a followingdescription, it is assumed that a mobility IP network protocol is aPMIP, but the present invention is not limited thereto. The presentinvention may be applied to other protocols, such as a dual stack mobileIP (DSMIP) protocol, GPRS tunneling protocol (GP), etc. In addition, inthe secondary RAT system, it is assumed that a data flow session for thesame PDN already exists. Further, the this present embodiment mayprovide a support that allows all data flows to be transmitted andreceived through the most appropriate RAT among multiple RAT systems,and such transmission may be defined as U-plane switch.

As described above, in order to provide seamless connectivity withrespect to a data flow in the simultaneous transmission scenario, a moreeffective handover scheme under a control of a network is required.Hereinafter, FIG. 8 shows methods for transmitting and receiving amessage to change routing information according to an embodiment of thepresent invention.

Here, in the present disclosure, it is assumed that a primary RAT systemis a 3GPP LTE system and a secondary RAT system is an IEEE 802.11(Wi-Fi) system, and some procedures may be modified to be applied asneeded for a newly defined communication system. Also, due to asimultaneous transmission scenario, it is assumed that a data flowsession is already present in the secondary RAT system as well as in theprimary RAT system. Here, in the primary RAT system, a general devicefalls to a state of EMM-Registered+ECM-Connected+RRC-Connected, and oneor more bearers retained by the corresponding device are activated.Also, in the secondary RAT system, a general device is in an associatedstate and transmits and receives data through a data flow session.

In the present invention, a method for moving (handover) a generaldevice having a session to which U-plane separation is applied or aparticular session/flow based on a primary RAT system control is asfollows. First, a serving BS may be changed from eNB 1 to eNB 2, androuting information of each session is changed as shown in Table 2 andTable 3.

TABLE 2 U-plane aggregation → U-plane U-plane aggregation → U-planesegregation switch Transmission RAT = Cellular Switch RAT = Cellular(eNB & AP → (eNB & AP → eNB) eNB) Transmission RAT = WiFi Switch RAT =WiFi (eNB & AP → (eNB & AP → AP) AP)

TABLE 3 U-plane segregation → U-plane U-plane segregation → U-planeaggregation switch Transmission RAT = Cellular Switch RAT = Cellular (AP→ eNB) (AP → eNB & AP) Transmission RAT = WiFi Switch RAT = WiFi (eNB →AP) (eNB → eNB & AP)

Here, in a case in which several flows are mapped within a singlebearer, when only a particular flow is determined to be routed, arouting type is set as a bandwidth aggregation. Also, in the 3GPPsystem, a UE and a P-GW share traffic flow description information,e.g., source and destination IP address and port numbers and theprotocol information, as a traffic flow template within protocolconfiguration options.

In the present invention, when a UE and a P-GW want to route only aparticular flow, they transmit traffic flow description information ofthe corresponding flow to start to provide (or inform) which flow of thecorresponding EPS bearer is to be routed. The reason for providing thenecessity of transmitting information to a different RAN cellular entity(e.g., eNBs) is because a serving/source BS of a general device may bechanged without changing a session(s) to which U-plane separation isapplied, and thus, a general device and a cellular entity (e.g., sourceeNB, MME, new entity) should transmit U-plane separation-relatedinformation of the corresponding device to a target BS during anexisting handover (HO) process.

According to the present invention, the U-plane separation-relatedinformation may include EPS bearer IDs to which U-plane separation hasbeen applied. Here, a different ID (e.g., E-RAB ID, DRB ID, LCID) mappedto the corresponding EPS bearer ID may be transmitted additionally or ina substituted manner. Also, the U-plane separation-related informationmay include U-plane separation-applied flow IDs, a routing type (U-planeaggregation/segregation/switch) with respect to each bearer/flow, arouting rule (transmission ratio through each RAT system/transmissionRAT/switch RAT) with respect to each bearer/flow, information (e.g.,BSSID, SSID, homogeneous extended SSID (HESSID), frequencychannel—operating class, channel number) regarding one or more entities(e.g., AP) performing data transmission and reception in a secondary RATsystem (e.g., WLAN/WiFi), signal strength measurement values of AP(s),etc.

Here, elements of systems affecting a change in routing information(e.g., flow ID, routing type/rule) may include load (cellular/WLAN),radio link quality (cellular/WLAN), QoS requirement, user preference,etc. According to values of the corresponding elements, routinginformation applied to a session may be changed or reapplied as shown inTable 4 below.

TABLE 4 Case 0 U-plane aggregation → U-plane aggregation Case 1 U-planeaggregation → U-plane segregation Case 2 U-plane aggregation → U-planeswitch Case 3 U-plane segregation → U-plane aggregation/switch Case 4U-plane segregation → U-plane switch

Hereinafter, a process of transmitting information related to U-planeseparation through a message according to a following interface isdescribed. A subject of transmitting the U-plane separation-relatedinformation is a source eNB. The U-plane separation-related informationis transmitted and received through a direct interface (e.g., X2)between a source eNB and a target eNB. Also, U-plane separation-relatedinformation may be transmitted using HO preparation information or an HOrequest message. Herein, as for the HO preparation information message,it is used to transfer the E-UTRA RRC information used by the target eNBduring handover preparation, including UE capability information. And,the HO request message is used to request the preparation of resourcesat the target side.

As illustrated in FIG. 8(a), the source eNB transmits HO preparationinformation including EPS bearer ID, DRB ID, routing type, routing rule,etc., to the target eNB (S810). Upon receiving the HO preparationinformation, the target eNB prepares handover.

As illustrated in FIG. 8(b), the source eNB transmits an HO Requestmessage including EPS bearer ID, routing type, routing rule, APinformation, etc., to the target eNB (S820), and the target eNBtransmits an ACK signal indicating that the foregoing information itemshave been normally received (S830).

As illustrated in FIG. 8(c), the U-plane separation-related informationmay be transmitted using an indirect interface (e.g., S1) between thesource eNB and the target eNB. For example, an HO required message & HOrequest message may be used. This message is used to request thepreparation of resources at the target side via the EPC. The source eNBtransmits an HO required message including EPS bearer ID, routing type,routing rule, etc., to an MME (S840), and upon receiving the HO requiredmessage from the source eNB, the MME transmits an HO request messageincluding EPS bearer ID, routing type, routing rule, etc., to the targeteNB (S850). The target eNB transmits an ACK signal to the MME in orderto indicate that the corresponding information items have been normallyreceived and handover is prepared (S860). The MME instructs the sourceeNB to perform handover through a handover command message (S870).

FIG. 9 shows a case in which a subject transmitting U-planeseparation-related information is an MME or a new entity.

Referring to FIG. 9(a), upon receiving a handover required messageindicating that handover needs to be performed from the source eNB(S900), the MME recognizes a bearer and a service type used in thesource eNB and transmits an HO request message including an EPS bearerID, a routing type, a routing rule, etc., to the target eNB (S910). Uponreceiving the corresponding information normally, the target eNBincludes information indicating that handover is ready in an ACK signaland transmits the same to the MME (S920). The MME instructs the sourceeNB to perform handover through a handover command message (S930). Thisis a scheme of further including U-plane separation-related informationin the existing HO request message and transmitting the same. Thismessage is used to request the preparation of resources at the targetside via the EPC.

Meanwhile, referring to FIG. 9(b), in the present invention, a secondaryRAT information request or a secondary RAT information request ACKmessage is newly defined, and information such as a bearer and a servicetype used by the corresponding device may be transmitted to the targeteNB by using these messages. The source eNB defines a cause value withrespect to a message generation as handover, and transmits a secondaryRAT information request message including information about a target eNBand AP information to the MME (S940). The MME checks the cause value,the information about the target eNB, and the AP information, andtransmits a secondary RAT information message including informationabout the source eNB, information about an EPS bearer ID of the deviceto be handed over, and AP information to the target eNB (S950). Thetarget eNB checks the EPS bearer ID and handover possibility, andincludes information indicating handover preparation completion in asecondary RAT information ACK and transmits the same to the MME (S960).The MME delivers the secondary RAT information ACK message to the sourceeNB and instructs handover (S970).

FIG. 10 shows an example of changing routing information of a session towhich U-plane aggregation is applied according to an embodiment of thepresent invention. In FIG. 10, a signaling flow in case of case 0(U-plane aggregation→U-plane aggregation) and case 1 (U-planeaggregation→U-plane segregation) is illustrated.

Referring to FIG. 10, a general device reports measurement results of asecondary RAT (e.g., WiFi) to an LTE system entity (1010). Here, the LTEsystem entity may include an eNB/MME, and a new entity capable ofcontrolling a bearer like an eNB/MME, when a new system are applied. Thegeneral device transmits identification information (e.g., BSSID, SSID,HESSID) for identifying a connected AP and signal strength measurementresults with respect to a corresponding AP(s). As a measurementconfiguration and report for transmission of the measurement results, amessage of an LTE system, e.g., RRCConnectionReconfiguration, UEMeasurement Report, may be used. Alternatively, in the presentinvention, for example, a secondary RAT measurement report may be newlydefined and measurement results may be included in the secondary RATmeasurement report message and transmitted. Here, for example, themeasurement configuration may include Type of measurement: Inter-RAT,Measurement report triggering: Inter RAT neighbor becomes better thanthreshold, etc.

Upon receiving the measurement report, the network (for example, the LTEsystem entity) determines whether routing information needs to bemodified based on QoS with respect to each bearer or a flow of bearers(QCI: quality class identifier, ARP: allocation and retention priority,bit rate of traffic per bearer, bit rates of traffic per group ofbearers) applied to U-plane aggregation owned by the correspondinggeneral device, WiFi and LTE signal measurement results reported by thegeneral device, and radio air/network load (1020). In this case, when itis determined that the routing information needs to be modified, the LTEsystem entity determines a routing type (=U-planeaggregation/segregation/switch) and a routing rule (transmission ratio,transmission RAT, switch RAT).

Thereafter, the LTE system entity transmits routing modify requestincluding following information to P-GW(s) corresponding to thedetermined PDN(s) (1030). The routing modify request information mayinclude EPS bearer IDs whose routing information is to be modified, flowIDs whose routing information is to be modified, a routing type (U-planeaggregation/segregation) of each EPS bearer/flow, a routing rule(transmission ratio, transmission RAT=cellular or WiFi) with respect toeach EPS bearer/flow, etc. In this case, by including all of routingrules for each routing type, the routing modify request information maybe utilized as information for a P-GW to finally determine a routingtype and a rule. For example, FIG. 10 shows a case in which a generaldevice receives user data from a P-GW1 and P-GW2. Here, the routingmodify request may be configured by adding other element informationrequired by a communication system to which the present invention isapplied, and a portion of the information may be removed when necessary.Also, the routing modify request information may be transmitted througha routing modify request message.

Upon receiving the routing modify request, the P-GW obtains a routingtype and rule with respect to a corresponding bearer/flow from a PCRF(1040). The PCRF, an entity that performs policy related to userbilling, handles a billing policy with respect to a service of thegeneral device.

Further, each P-GW determines whether to modify a corresponding bearerand a routing type/rule (1050) based on routing type/rule obtained fromthe LTE system entity and the PCRF. In a case in which several flows aremapped to a single bearer, when routing information of only a particularflow is determined to be modified, each P-GW sets a routing type asU-plane aggregation as is.

Each P-GW informs the LTE system entity about the results, namely,whether a bearer has been modified and about the routing type/rule(1060). The modified information may be transmitted through a routingmodify response message. The routing modify information may include aresponse (accept/reject) with respect to a request from the LTE systementity, EPS bearer ID whose routing information needs to be modified,flow ID whose routing information needs to be modified, etc.

Here, in the 3GPP system, the UE and the P-GW share traffic flowdescription information (e.g., source and destination IP address andport numbers and the protocol information) as traffic flow templatewithin protocol configuration options. Also, in a case in which routinginformation of only a particular flow is determined to be modified, eachP-GW may deliver traffic flow description information to be modified,thereby informing the UE about how which flow within a corresponding EPSbearer is routing-modified.

Also, the routing modify information may further include informationabout a routing type which indicates a type of simultaneous transmissionto be modified in each EPS bearer/flow (U-planeaggregation/segregation), and a routing rule which indicates asimultaneous transmission rule to be modified in each EPS bearer/flow(in case of U-plane aggregation, transmission through each RAT system/incase of U-plane segregation, transmission RAT)

When the result within the received response message is ‘accept’, theLTE system entity temporarily stores the information for modifyingsimultaneous transmission of the general device (e.g., a P-GW to whichsimultaneously transmission is to be applied, etc.). Also, when theresult is ‘accept’, the LTE system entity informs the general deviceabout the simultaneous transmission modify information (1070). Therouting modify information is transmitted through a routingconfiguration modify request message, and the message may include EPSbearer ID whose routing information is to be modified, flow ID whoserouting information is to be modified, routing type which indicates atype of simultaneous transmission to be modified in DRB/EPS bearer/flow(U-plane aggregation/segregation), routing rule which indicates asimultaneous transmission rule to be modified in each DRB/EPSbearer/flow (in case of U-plane aggregation, a transfer rate througheach RAT system/in case of U-plane segregation, transmission RAT). Here,with respect to the EPS bearer ID, the LTE system entity mayadditionally or transmit any other ID (e.g., E-RAB ID, DRB ID, LCID)mapped to the corresponding EPS bearer ID in a substituted manner.

In response to the request message, the general device may transmit arouting configuration modify response message to the LTE system entity(1080). The routing configuration modify response message may include aresult which indicates a response with respect to a request from the LTEsystem entity (accept/reject) and information regarding recommended EPSbearer ID/flow ID/routing type/routing rule.

Here, when the result is ‘reject’, the general device may include thecorresponding reject information. Meanwhile, when the result is‘accept’, the general device applies modified routing information to ULdata of a corresponding bearer/flow.

The LTE system entity may perform different procedures according to aresponse message received from the general device.

First, in the case in which the result within the response message is‘accept’, the LTE system entity informs the P-GW about the fact by usinga routing configuration modify complete message (1090). When the resultis ‘accept’, the P-GW applies the modified routing information to DLdata of corresponding bearer/flow.

Meanwhile, when the result within the response message is ‘failure’ andthe recommended information is not included, the LTE system entityrequests the corresponding P-GW(s) to cancel the previous routing modifyrequest (step 1030), and deletes the contents temporarily stored in step1070. Upon the receipt of it, the P-GW(s) cancels the correspondingmodify request (1090).

Also, when the result within the received response message is ‘failure’and the recommended information is included, the LTE system entityperforms the procedure of step 1030 according to the recommendedinformation (1091) and informs the general device about the result(1092). Here, the LTE system entity provides the result, EPS bearer ID,etc., through a routing configuration modify command message. Thus, thegeneral device applies the modified routing information to UL data of acorresponding bearer/flow. Here, the result with respect to therecommended information includes information requested by the generaldevice.

In addition, in a case in which a routing type to be modified is U-planesegregation and there is no more data to be transmitted i) through acorresponding EPS bearer (cellular session) or ii) through a WiFisession mapped to the corresponding EPS bearer, the following additionaloperation (success case) may be performed.

First, in a case that there is no more data to be transmitted through acorresponding EPS bearer (cellular session), and the general devicemoves to the WiFi system, the following operations may performed. Here,a case in which the default bearer is U-plane separated to the WiFisystem and a dedicated bearer is still maintained in the LTE system maybe excluded. Namely, when an EPS bearer which is U-plane separated to aWiFi system corresponds to a linked EPS bearer ID of any other EPSbearer operating in the LTE system, the process may not be performed.

The P-GW or the LTE system entity (e.g., MME) releases or deactivatesthe corresponding EPS bearer. Also, E-RAB ID and DRB ID/LCID (allocatedby eNB) mapped to the corresponding EPS bearer are released/deactivatedtogether by the LTE system entity (e.g., MME, eNB). The DRB ID/LCIDrelease may be configured by using, e.g., RRCConnectionReconfigurationof the LTE system procedure. When the message is received, the generaldevice stops transmitting the UL data. Also, E-RAB ID release may beconfigured by using, e.g., E-RAB RELEASE COMMAND, E-RAB ReleaseINDICATION.

On the other hand, in a case that there is no more data to betransmitted through a WiFi session mapped to a corresponding EPS bearer,and the general device moves to the LTE system, the P-GW or the LTEsystem entity releases/deactivates a WiFi session mapped to thecorresponding EPS bearer. Here, in the case of modifying the routingtype to U-plane segregation, a routing type may be explicitly set toU-plane segregation, but it may be implicitly informed by modifyingtransmission ratio with respect to one RAT to 0 in routing rule.

So far, the case in which routing modification is requested by a networkhas been described in FIG. 10. FIG. 11 shows a case in which routingmodification is requested by a general device according anotherembodiment of the present invention. It is obvious that transmission ofthe same information in the same steps as those of FIG. 10 is included,and hereinafter, only steps added according to determination of thegeneral device are additionally described.

Referring to FIG. 11, after the general device reports measurementresult with respect to secondary RAT (e.g., WiFi) to the LTE systementity (1010), the general device transmits a routing configurationmodify request message including routing modify information to the LTEsystem entity (1115). The routing configuration modify request messageincludes information regarding EPS bearer, routing type, routing rule,etc. This includes information that a request for modifying routingstarts by the general device.

The LTE system entity checks the received routing modify informationthrough the request message, determines whether the correspondingrouting needs to be modified (1020), and subsequently transmits arouting configuration modify response message including results withrespect to whether to modify routing according to the routing modifyinformation to the general device (1025). In FIG. 11, for example, acase in which the result as to modification is reject is shown, and whenthe modify result is accepted, a response message including modifiedrouting modify information may be transmitted.

Meanwhile, in response to the routing modify request message (1015), theLTE system entity may perform a routing configuration modify procedurewith each P-GW (steps 1030 to 1060 as the modify procedure are the sameas those of FIG. 10 described above), and transmit a routing responsemessage including a result, recommended routing type/routing rule to thegeneral device (1080). The routing response message includes informationregarding routing modification requested by the general device. As anacknowledgement with respect to the response message, the general devicetransmits a routing configuration modify command message to the LTEsystem entity (1092). The routing configuration modify command messagemay include a result, EPS bearer ID, etc.

In addition, when routing modify is rejected by the general device, theLTE system entity may request the corresponding P-GW(s) to cancel theprevious routing modify request (cancel is identified by EPS bearer ID)(1094). Also, when routing modify is accepted, a routing modify complete(modify complete is identified by EPS bearer ID) may be requested(1096).

FIG. 12 shows a signaling flow in case 2 (U-plane aggregation→U-planeswitch) according to an embodiment of the present invention. Referringto FIG. 12, the same procedure as that of FIG. 10 is performed, andinformation included in some steps may be different.

The general device reports the measurement result with respect to thesecondary RAT (e.g., WiFi) to the LTE system entity (1010). Here, themeasurement result report includes identification information (e.g.,BSSID, SSID, HESSID) for identifying an accessed AP and a signalstrength measurement result with respect to corresponding AP(s). This isthe same as step 1010 of FIG. 10.

The LTE system entity determines whether routing information needs to bemodified (1020). This includes step 1020 of FIG. 10. Thereafter, the LTEsystem entity transmits a routing modify request including the followinginformation to P-GW(s) corresponding to all the PDN(s) owned by acorresponding device according to the determined routing type (=U-planeswitch) (1030).

The routing modify request includes a routing type (U-plane switch), arouting rule which indicates U-plane separation rule to be modified(=switch RAT: cellular (to eNB)/WiFi (to AP)). In this case, the routingmodify request may include all the routing rules with respect to otherrouting types (bandwidth aggregation/segregation), so that the P-GW mayutilize the information in finally determining a single routing type andrule.

Upon receiving the routing modify request, each P-GW obtains a routingtype and rule with respect to the corresponding bearer/flow from thePCRF (1040), and determines whether to modify with respect to thecorresponding bearer and routing type/rule (1050). Each P-GW informs theLTE system entity about the result (1260). The routing modify responseincludes information regarding a result which indicates a response(accept/reject) with respect to a request from the LTE system entity,routing type which indicates U-plane separation type to be modified(=U-plane switch), routing rule which indicates U-plane separation ruleto be modified (switch RAT).

When the result within the received message is ‘accept’, the LTE systementity temporarily stores modify information for U-plane switch of thegeneral device, and provides the modify information for U-plane switchto the general device. The modify information is transmitted through arouting configuration modify request message, and the message includesrouting type which indicates U-plane separation type to be modified(=U-plane switch) and routing rule which indicates U-plane separationrule to be modified (switch RAT).

The general device may transmit a routing configuration modify responsemessage in response to the request message (1280). The response messagemay include a result which indicates a response (accept/reject) withrespect to a request from the LTE system entity and a recommendedrouting type/routing rule. Hereinafter, steps 1090 and 1095 are the sameas those shown in FIG. 10.

In addition, in the present invention, a session suspend timer may bedefined. At a time point at which the routing modify is successfullycompleted, the general device and the LTE system entity starts thesession suspend timer. If there is no modification (e.g., re-switch)until the corresponding timer expires, a bearer/session mapped to an EPSbearer of a previous RAT is suspended according to a switch RAT.

Also, in the present invention, a session release timer may be defined.At a time point at which the routing modification is successfullycompleted or at a time point at which the session suspend timer isterminated, the general device and the LTE system entity starts thesession release timer. If there is no modification until thecorresponding timer expires, a bearer/session mapped to the EPS bearerof a previous RAT is released according to a switch RAT.

Meanwhile, in the present invention, when a switch RAT is WiFi in therouting rule, the following procedure may be performed. The LTE systementity (e.g., eNB) suspends (deactivates)/releases radio bearers mappedto all the EPS bearers related to U-plane. In this case, an existingradio bearer release procedure of the LTE system is used. Here, when theRRC_CONNECTED of the general device is intended to be maintained, RRCConnection Reconfiguration may be used. When the general device isintended to be transit to the RRC_IDLE, RRC Connection Release may beused. In this case, after receiving UE context release command, the eNBmay transmit RRC connection release. In this case, release cause may bedefined as U-plane switch.

Also, the LTE system entity (e.g., eNB, MME) suspends(deactivates)/releases E-RAB mapped to the corresponding EPS bearer. Inthis case, the existing release procedure of the LTE system is used.Here, when the RRC_CONNECTED of the general device is intended to bemaintained, E-RAB RELEASE COMMAND/E-RAB Release INDICATION may be used.Also, when the general device is intended to be transit to the RRC_IDLE,UE context release request/UE context release command may be used. Inthis case, release access bearer request/release access bearer responsemay be used between the MME and the S-GW.

Meanwhile, when the switch RAT is cellular in the routing rule, the P-GWor the LTE system entity suspends (deactivates)/releases a WiFi sessionmapped to all the EPS bearers related to the U-plane.

FIG. 13 shows a signaling flow in case 3 (U-plane segregation→U-planeaggregation) according to an embodiment of the present invention.Hereinafter, a portion of the procedure of FIG. 13 may be the same asthat of FIG. 10, and information included in some steps may bedifferent.

First, in a case in which a transmission RAT currently applied to acorresponding session is cellular, a routing information modifyprocedure is the same as the case 0 & 1. Meanwhile, in a case in which atransmission RAT currently applied to a corresponding session is WiFi, arouting information modify procedure is identical to case 3.

During a process of generating a PDN connection through a secondary RATsystem, the P-GW may newly allocate resources for the corresponding PDNconnection and set QoS, or may be mapped to an existing resource. Sincethe corresponding PDN connection is a user data pathgenerated/transmitted through the secondary RAT system, rather than aprimary RAT system, there is no need to perform all the procedures(e.g., resource allocation related to a radio bearer, resourceallocation between eNB and S-GW, etc.). Thus, information indicatingfact that the PDN connection is generated through the secondary RATsystem needs to be transmitted to the S-GW/MME.

Here, resources for PDN connection and QoS parameters may includeinformation such as EPS bearer ID (in create session request sent byMME, in create bearer response sent by MME), PDN connection ID, QCI,ARP, guaranteed bit rate (GBR), maximum bit rate (MBR), access pointname aggregate maximum bit rate (APN-AMBR), UE-AMBR, etc.

In case of the PDN connection ID, a new identifier for the correspondingpurpose may be defined, rather than utilizing an existing EPS bearer ID.In this case, a subject allocating the corresponding identifier may bethe MME or the P-GW, and in the procedure related to sessiongeneration/change for (re)applying U-plane segregation, whether theidentifier is an EPS bearer ID or whether it is an identifier of thecorresponding purpose needs to be discriminated and informed to arecipient. Also, information (e.g., EPS bearer ID, PDN connection ID,QoS) regarding the corresponding PDN connection is transmitted to othercellular entities (e.g., eNB, MME, new entity), as well as to thegeneral device. This may be limited to only a case in which resource isnewly allocated.

Thus, each P-GW informs the LTE system entity about the result of step1050. The LTE system entity receives a routing modify request message(1360). The routing modify request message includes a result whichindicates a response (accept/reject) with respect to a request from theLTE system entity, EPS bearer ID, flow IDs whose routing information isto be modified, a routing type which indicates U-plane separation typeto be modified with respect to each EPS bearer/flow (U-planeaggregation/segregation), a routing rule which indicates U-planeseparation rule to be modified with respect to each EPS bearer/flow (incase of U-plane aggregation, transfer rate through each RAT system/incase of U-plane segregation, transmission RAT). The EPS bearer IDincludes a source mapping EPS bearer ID for EPS bearer whose routinginformation is to be modified, and a target mapping EPS bearer ID forEPS bearer to be used for transmission and reception of user databelonging to a corresponding source mapping EPS bearer. In this case,when the target mapping EPS bearer ID is identical to the source mappingEPS bearer ID, the target mapping EPS bearer ID may be omitted.

In a case in which the result within the received routing modify messageis ‘accept’ in step 1360, the LTE system entity temporarily storesinformation for simultaneous transmission modification of the generaldevice (e.g., the P-GW to which simultaneous transmission is to beapplied, etc.), and provides the simultaneous transmission modifyinformation (1370). The routing configuration modify request messageincludes EPS bearer ID (source mapping EPS bearer ID, target mapping EPSbearer ID), Flow ID whose routing information is to be modified, arouting type which indicates U-plane separation type to be modified ineach DRB/EPS bearer/flow, and a routing rule which indicates U-planeseparation rule to be modified in each DRB/EPS bearer/flow. Here, theLTE system entity may additionally or in a substituted manner transmitother IDs (e.g., E-RAB ID, DRB ID, LCID) mapped to the corresponding EPSbearer ID. Thereafter, when the general device determines that theresult is ‘accept’, the general device applies the modified routinginformation to UL data of a corresponding bearer/flow (1380). Thus, thegeneral device may transmit a routing configuration modify responsemessage including information regarding the routing modify request tothe LTE system entity.

Meanwhile, when the result within the received message is ‘accept’, theLTE system entity informs the P-GW accordingly (1395). When the resultis ‘accept’, the P-GW applies the modified routing information to DLdata of the corresponding bearer/flow.

Here, when the source mapping EPS bearer ID and target mapping EPSbearer ID are different from each other, the P-GW release the sourcemapping EPS bearer ID. This is because, in the case in which user databelonging to the source mapping EPS bearer is intended to be transmittedand received by mapping it to an existing bearer in which datatransmission and reception is already performed through a cellularnetwork, the source mapping EPS bearer ID is not necessary any longerafter the bearer mapping is normally completed.

FIG. 13 shows a case in which a routing modify request is NW-initiatedand a case of mapping to an existing bearer in which data transmissionand reception is already performed through a cellular network.Meanwhile, FIG. 14 shows a case in which routing modify is requestedaccording to NW initiation and a new bearer is generated and a case inwhich a dedicated bearer is established according to an embodiment ofthe present invention. Hereinafter, the same numbered steps in FIG. 14are identical to the steps described above with reference to FIGS. 10 to13, and only some steps including different information are described.

Referring to FIG. 14, step 1412 is included only in a case in which whena transmission RAT currently applied to a corresponding session is WiFi,and a UE intends to modify routing information (e.g., U-planesegregation→U-plane aggregation, U-plane segregation transmissionRAT=cellular). It may also be defined as UE initiated routing change. Itis assumed that the UE, a general device, requests generation of adedicated bearer as a bearer to be used in a cellular network. When theUE requests generation of a default bearer as a bearer to be used in thecellular network, a PDN CONNECTIVITY REQUEST message is used. Thus, aPDN CONNECTIVITY REQUEST and ACTIVATE DEFAULT EPS BEARER CONTEXT REQUESTare used between the UE and the MEE, and a create session request,create session response may be used between the MME and the GW.

Thus, the LTE system entity transmits a dedicated bearer generationrequest including the following information to P-GW(s) corresponding tothe PDN(s) determined in step 1020 (1430). In this case, although thereis no message reception in step 1412, the LTE system entity may transmitthe corresponding request to the P-GW(s). Define this as NW initiatedrouting change 1. In this case, the request message may include EPSbearer IDs for modifying routing information, flow IDs for modifyingrouting information, routing type with respect to each EPS bearer/flow(U-plane aggregation/segregation), routing rule with respect to each EPSbearer/flow (transmission ratio, transmission RAT=cellular or WiFi). Inthis case, by including all the routing rules with respect to eachrouting type, the message may be utilized as information for the P-GW tofinally determine a single routing type and rule.

After performing determination on the routing type/rule, each P-GWtransmits a dedicated bearer generation request including the result tothe MME (1460). In this case, even without the dedicated bearergeneration request from the LTE system entity, each P-GW may transmitthe corresponding request. Define this as NW initiated routing change 2.

The dedicated bearer generation request may include a result whichindicates response (accept/reject) with respect to a request from theLTE system entity, EPS bearer ID for EPS bearer for modifying routinginformation, flow ID for flow for modifying routing information, arouting type which indicates simultaneous transmission type to bemodified in each EPS bearer/flow (U-plane aggregation/segregation), arouting rule which indicates simultaneous transmission rule to bemodified in each EPS bearer/flow (in case of U-plane aggregation,transfer rate through each RAT system/in case of U-plane segregation,transmission RAT), etc. As for the flow ID, the UE and the P-GW in the3GPP system share traffic flow description information (e.g., source anddestination IP address and port numbers and the protocol information) astraffic flow template within protocol configuration options. Also, in acase in which routing information of only a particular flow isdetermined to be modified, the P-GW transmits traffic flow descriptioninformation to be modified, thereby informing the UE about which flowwithin a corresponding EPS bearer is modified. Upon receiving thecorresponding request, the MME generates E-RAB for the correspondingdedicated bearer between the eNB and the S-GW.

When the result within the bearer configuration request message is‘accept’, the LTE system entity temporarily stores information forsimultaneous transmission modification of the general device (e.g., P-GWto which simultaneous transmission is to be applied, etc.), and providesthe simultaneous transmission modification (1470).

During the process, the eNB and the UE generate a radio bearer for thecorresponding dedicate EPS bearer. It includes the EPS bearer ID for EPSbearer for modifying routing information, flow ID for flow for modifyingrouting information, a routing type which indicates simultaneoustransmission type to be modified in each DRB/EPS bearer/flow, a routingrule which indicates simultaneous transmission rule to be modified ineach DRB/EPS bearer/flow (in case of U-plane aggregation, transfer ratethrough each RAT system/in case of U-plane segregation, transmissionRAT), etc. Here, with respect to the EPS bearer ID, the LTE systementity may additionally or in a substituted manner transmit other IDs(e.g., E-RAB ID, DRB ID, LCID) mapped to the corresponding EPS bearerID. This may be performed through an RRC connection reconfigurationmessage.

When the result is ‘accept’, the general device applies the modifiedrouting information to UL data of the corresponding bearer/flow (1080).By transmitting the RRC connection reconfiguration complete message,information about the application completion is provided.

Also, the general device transmits results of performing steps 1470 and1480 to the LTE system entity (e.g., MME). In this case, the generaldevice requests a session management from the MME through a directtransfer/session management response message. In this case, in responseto the session management, the LTE system entity transmits a responsemessage including the corresponding EPS bearer ID to the correspondingP-GW(s) in step 1490. Namely, when the result within the received instep 1480 is ‘accept’, the LTE system entity informs the P-GWaccordingly. In this case, the transmitted EPS bearer ID includes anidentifier (=source EPS bearer) of a bearer for modifying routinginformation and an identifier (=target EPS bearer) of a bearer which hasbeen newly generated to be used in the cellular network. The target EPSbearer ID is an identifier allocated by the LTE system entity (e.g.,MME). The P-GW applies the modified routing information to DL data ofthe corresponding bearer/flow.

FIG. 15 shows a signaling flow in case 4 (U-plane segregation→U-planeswitch) according to an embodiment of the present invention.Hereinafter, steps numbered to be identical to those of FIG. 10 are thesame as the steps described above with reference to FIGS. 10 to 14, andonly some steps including different information are described.

First, in a case in which a switch RAT is WiFi, a routing informationmodify procedure is the same as case 2.

Meanwhile, in a case in which a switch RAT is cellular, a routinginformation modify procedure is the same as case 4. In this case, duringa process of generating a PDN connection through a secondary RAT system,a P-GW newly allocates resources for corresponding PDN connection andsets QoS, or maps it to the existing resource. This is because, sincethe corresponding PDN connection is a user data pathgenerated/transmitted through the secondary RAT system, rather than theprimary RAT system, there is no need to perform all the procedures(e.g., resource allocation related to a radio bearer, resourceallocation between eNB and S-GW, etc.). Thus, information indicatingfact that the PDN connection is generated through the secondary RATsystem needs to be transmitted to the S-GW/MME.

In this case, resource for the PDN connection and QoS parameters includeEPS bearer ID (in create session request sent by MME, in create bearerresponse sent by MME), QCI, ARP, GBR, MBR, APN-AMBR, UE-AMBR, etc.Information regarding the corresponding PDN connection is transmitted toother cellular entities (e.g., eNB, new entity), as well as to thegeneral device. This may be limited only to a case in which resource isnewly allocated.

Referring to FIG. 15, each P-GW informs the LTE system entity about theresult in step 1560. In this case, a routing modify response message mayinclude a result which indicates a response (accept/reject) with respectto a request from the LTE system entity, a routing type which indicatesU-plane separation type to be modified (=U-plane switch), a routing rulewhich indicates U-plane separation rule to be modified (switch RAT), QoSmapping information, etc.

Here, the QoS mapping information may include, when mapped to anexisting bearer in which data transmission and reception is alreadyperformed through the cellular network, a source mapping EPS bearer IDfor EPS bearer for modifying routing information and a target mappingEPS bearer ID for EPS bearer to be used for transmitting and receivinguser data belonging to a corresponding the source mapping EPS bearerwhen routed to the cellular network, and in this case, when the targetmapping EPS bearer ID is identical to the source mapping EPS bearer ID,the target mapping EPS bearer ID may be omitted. The QoS mappinginformation may include, when mapped to a newly generateddefault/dedicated bearer, the source mapping EPS bearer ID for EPSbearer for modifying routing information, and action code for generationof default/dedicated bearer, and the P-GW transmits a request forperforming according to Action code to the MME.

In this case, the P-GW may not transmit DL data to a previous RAT.

FIG. 16 is a block diagram showing a wireless communication systemaccording to an embodiment of the present invention.

A network entity (including BS, MME, GW) 1650 includes a processor 1651,a memory 1652, and a radio frequency (RF) unit 1653. The memory 1652 iscoupled to the processor 1651, and stores a variety of information fordriving the processor 1651. The RF unit 1653 is coupled to the processor1651, and transmits and/or receives a radio signal. The processor 1651implements the proposed functions, procedures, and/or methods. In theembodiments of FIG. 2 to FIG. 15, the operation of the network entitycan be implemented by the processor 1651.

Especially, the processor 1651 may configure one or more cells withdifferent frequencies or systems including Cellular/Wi-Fi, for thisinvention the processor 1651 may configures U-plane configuration havinga WLAN triggering condition, a measurement configuration, and/or radiobearer configuration with the Wi-Fi system as the secondary system.

The processor 1651 may configure information on routing modification,the information on routing modification includes information on bearerID including an EPS bearer ID, an E-RAB ID, a DRB ID, an LCID, a dataflow ID, information on a routing type to be applied to a correspondingbearer and data flow, wherein the routing type includes at least one aU-plane aggregation, a U-plane segregation and a U-plane switch.

The information on the routing modification is changeable and varied byat least one of a network preference including a primary RAT system orthe secondary RAT system, a quality of service (QoS) information, andbearer information. Also the threshold can be defined based on dataamount, data characteristic (type), or data QoS.

The routing type includes a routing type transition. The routing typetransition includes a case, which is from a U-plane aggregation toU-plane aggregation, from a U-plane aggregation to U-plane segregation,from a U-plane aggregation to a U-plane switch, from a U-planesegregation to a U-plane aggregation or a U-plane segregation, or from aU-plane segregation to a U-plane switch.

Also the information on a routing rule includes that a ratio oftransmission for a corresponding bearer and data flow is applied to theprimary RAT system and secondary RAT system, wherein the routing ruleincludes an indication of a transmission RAT system. The primary RATsystem is a 3GPP LTE system, and wherein the secondary RAT system isIEEE 802.11 system.

The processor 1651 may configure the information and control datatransition direction between the primary RAT system and the secondaryRAT system, it uses network preference information of UE including anavailable AP, a preferred AP, or a private AP, wherein the priority isdetermined by a load and a service set of the APs each. The processor1651 may configure the information, the information further includes aconfiguration including whether a condition is setup, modified orreleased of the data bearer for the UE.

Thus the processor 1651 may have a signal procedure having theconfigured the information with UE, the processor 1651 control totransmit and receive the information on routing modification andinformation on the handover according to the information, it includesRRC message including a measurement configuration/report, a radioresource bearer configuration/complete, a handover procedure messageswith UE.

The wireless device 1660 includes a processor 1661, a memory 1662, andan RF unit 1663. The memory 1662 is coupled to the processor 1661, andstores a variety of information for driving the processor 1661. The RFunit 1663 is coupled to the processor 1661, and transmits and/orreceives a radio signal. The processor 1661 implements the proposedfunctions, procedures, and/or methods. In the embodiments of the FIG. 2to FIG. 13, the operation of the UE can be implemented by the processor1661.

Especially, the processor 1661 may configure one or more cells withdifferent frequencies or systems including Cellular/Wi-Fi, for thisinvention the processor 1651 may configures U-plane configuration havinga WLAN triggering condition, a measurement configuration, and/or radiobearer configuration with the Wi-Fi system as the secondary system. Theprocessor 1661 may check an configure information on routingmodification, the information on routing modification includesinformation on bearer ID including an EPS bearer ID, an E-RAB ID, a DRBID, an LCID, a data flow ID, information on a routing type to be appliedto a corresponding bearer and data flow, wherein the routing typeincludes at least one a U-plane aggregation, a U-plane segregation and aU-plane switch.

The processor 1661 may check that the information on the routingmodification is changeable and varied by at least one of a networkpreference including a primary RAT system or the secondary RAT system, aquality of service (QoS) information, and bearer information. Also thethreshold can be defined based on data amount, data characteristic(type), or data QoS. For this the UE can send the QoS measurementresult, and UE preference network information to the network entity. Theinformation on the routing modification includes a routing type, itincludes a routing type transition, the routing type transition includesa case, which is from a U-plane aggregation to U-plane aggregation, froma U-plane aggregation to U-plane segregation, from a U-plane aggregationto a U-plane switch, from a U-plane segregation to a U-plane aggregationor a U-plane segregation, or from a U-plane segregation to a U-planeswitch. Also the information on a routing rule includes that a ratio oftransmission for a corresponding bearer and data flow is applied to theprimary RAT system and secondary RAT system, wherein the routing ruleincludes an indication of a transmission RAT system. So the UE cansupports that the primary RAT system is a 3GPP LTE system, and whereinthe secondary RAT system is IEEE 802.11 system.

The processor 1661 may configure the information and control datatransition direction between the primary RAT system and the secondaryRAT system, it may send a recommended information including a bearer ID,data flow ID, a routing type, and a routing rule for the datatransmission. It includes network preference information of UE includingan available AP, a preferred AP, or a private AP, wherein the priorityis determined by a load and a service set of the APs each. The processor1661 may configure the information, the information further includes aconfiguration including whether a condition is setup, modified orreleased of the data bearer for the UE.

Thus the processor 1661 may have a signal procedure having theconfigured the information with UE, the processor 1661 control totransmit and receive the information on routing modification andinformation on the handover according to the information, it includesRRC message including a measurement configuration/report, a radioresource bearer configuration/complete, a handover procedure messageswith the network entity.

The processor may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Thememory may include read-only memory (ROM), random access memory (RAM),flash memory, memory card, storage medium and/or other storage device.The RF unit may include baseband circuitry to process radio frequencysignals. When the embodiments are implemented in software, thetechniques described herein can be implemented with modules (e.g.,procedures, functions, and so on) that perform the functions describedherein. The modules can be stored in memory and executed by processor.The memory can be implemented within the processor or external to theprocessor in which case those can be communicatively coupled to theprocessor via various means as is known in the art.

In the above exemplary systems, although the methods have been describedon the basis of the flowcharts using a series of the steps or blocks,the present invention is not limited to the sequence of the steps, andsome of the steps may be performed at different sequences from theremaining steps or may be performed simultaneously with the remainingsteps. Furthermore, those skilled in the art will understand that thesteps shown in the flowcharts are not exclusive and may include othersteps or one or more steps of the flowcharts may be deleted withoutaffecting the scope of the present invention.

What is claimed is:
 1. A method for performing, by a user equipment(UE), routing modification in a wireless communication system, themethod comprising: receiving information on routing modification from anetwork entity of a primary radio access technology (RAT) system; andperforming the routing modification between the primary RAT system and asecondary RAT system according to the information on routingmodification, wherein the secondary RAT system is used for user plane(U-plane) data, wherein the primary RAT system is a 3rd GenerationPartnership Project (3GPP) Long-Term Evolution (LTE) system, wherein thesecondary RAT system is an Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 system, and wherein the information on routingmodification further includes information on bearer identity (ID)including an evolved packet system (EPS) bearer ID and a data radiobearer (DRB) ID, and a logical channel ID (LCID).
 2. The method of claim1, wherein the information on routing modification further includesinformation on a routing type to be applied to a corresponding bearerand data flow, and wherein the routing type includes at least one aU-plane aggregation, a U-plane segregation and a U-plane switch.
 3. Themethod of claim 2, wherein the information on routing modification ischanged adaptively according to a routing type transition, and whereinthe routing type transition includes a case, which is from a U-planeaggregation to U-plane aggregation, from a U-plane aggregation toU-plane segregation, from a U-plane aggregation to a U-plane switch,from a U-plane segregation to a U-plane aggregation or a U-planesegregation, or from a U-plane segregation to a U-plane switch.
 4. Themethod of claim 1, wherein the information on routing modificationfurther includes information on a routing rule including that a ratio oftransmission for a corresponding bearer and data flow is applied to theprimary RAT system and secondary RAT system, wherein the routing ruleincludes an indication of a transmission RAT system.
 5. The method ofclaim 1 further comprising: transmitting a response message, in responseto the information on routing modification, to the network entity of theprimary RAT system.
 6. The method of claim 5, wherein the responsemessage further includes recommended information including a bearer ID,a data flow ID, a routing type, and a routing rule.
 7. The method ofclaim 1 further comprising: starting a session suspend timer afterperforming the routing modification, and starting a session releasetimer after performing the routing modification or after the sessionsuspend timer expires.
 8. The method of claim 1 further comprising:transmitting measurement results configured for the secondary RATsystem, wherein the measurement results further include informationincluding a priority of access points (APs) of the secondary RAT system,and preference information including an available AP, a preferred AP, ora private AP.
 9. A wireless device in a wireless communication system,the wireless device comprises: a radio frequency (RF) unit; and aprocessor, coupled to the RF unit, that: receives information on routingmodification from a network entity of a primary radio access technology(RAT) system; and perform the routing modification between the primaryRAT system and a secondary RAT system according to the information onrouting modification, wherein the secondary RAT system is used for auser plane (U-plane) data, wherein the primary RAT system is a 3rdGeneration Partnership Project (3GPP) Long-Term Evolution (LTE) system,wherein the secondary RAT system is an Institute of Electrical andElectronics Engineers (IEEE) 802.11 system, and wherein the informationon routing modification further includes information on bearer identity(ID) including an evolved packet system (EPS) bearer ID and a data radiobearer (DRB) ID, and a logical channel ID (LCID).